Kinetika Pertumbuhan Aspergillus oryzae KKB4 pada Substrat Padat serta Aktivitas Enzim Kasar Ekstraseluler untuk Mereduksi Aflatoksin B

https://doi.org/10.22146/agritech.9785

Sardjono Sardjono(1*)

(1) Fakultas Teknologi Pertanian, Universitas Gadjah Mada, Jl. Sosio Yustisia, Bulaksumur, Yogyakarta 55281
(*) Corresponding Author

Abstract


Previous research indicated that Aspergillus oryzae KKB4 be able to degrade aflatoxin B  (AFB1) and it was found 1that extracelular enzymes take a role on degrading and detoxify AFB1 in submerged culture system. Fungal fermenta-tion in solid-state culture more advantage compare to submerged culture system, because of the medium composition is simple and relatively cheaper than submerged culture. Agricultural waste usually used for solid-state culture system for fungal fermentation. The growth kinetics of Aspergillus oryzae KKB4 in solid-state culture and its extracellular enzyme activity were observed in this research. Rice bran was used for growth medium. The inoculated rice bran were aseptically distributed over petridishes containing 29-30 g of inoculated rice bran. Incubation was carried out in an incubator at 27 oC and relative humidity of 87-95 %. Kinetic parameters were studied, i.e. biomass, measured by bio- mass protein and viable plate count method, spore concentration, carbondioxide production rate (CPR), lost of water and dry matter, and the activity of crude extracellular enzyme againts AFB1. Crude extracellular enzyme was extractedfrom fermented rice bran by using 0.05M phosphate buffer and pure AFB1 was used as substrate. The reaction was conducted at 30 oC for 1 hr. It was shown that growth pattern was different between viable plate count and biomass protein. The biomass protein increased until the end of fermentation, and the maximum biomass protein was 2.628 mg/g dry matter. The maximum specific growth rate was 0.022/hr, and the highest carbon dioxide production rate (CPR) was0.0324 mmole/g/day found in the third day of fermentation. The metabolic activities also be shown by the rate of dry matter lost. The highest rate of dry matter lost also found in the third day of fermentation, and the correlation between dry matter lost and CPR was expressed in equation of y = 1.185 x + 0.0079. This result indicated that metabolic activi- ties (CPR, lost of dry matter) was able to be used as the growth parameter. The activity of crude extracellular enzyme associated with the fungal growth, and the highest activity was observed in the third day fermentation, it was 1.699 µg AFB1/ml/hr, or 0.888 µg AFB1/g biomass protein/hr.

ABSTRAK

Penelitian terdahulu menunjukkan bahwa Aspergillus oryzae KKB4, mampu mendegradasi aflatoksin B  (AFB1)  dan 1diketahui bahwa enzim ekstraseluler berperan dalam mendegradasi dan detoksifikasi AFB1 dengan menggunakansistem kultur rendam. Fermentasi jamur dengan substrat padatmemiliki beberapa keunggulan dibandingkan dengan kultur rendam, terutama karena media yang digunakan lebih murah. Hal ini disebabkan karena dapat mengguna- kan limbah pertanian sebagai media fermentasi. Dalam penelitian ini dilihat kinetika petumbuhan Aspergillus oryzae KKB4 pada substrat padat dan aktivitas enzim kasar ekstraluler terhadap penurunan AFB1. Sebagai media fermentasi digunakan dedak steril. Setelah inokulasi, dedak didistribusikan secara aseptis pada cawan petri sebanyak 29-30 gram tiap petri. Inkubasi dilakukan pada suhu 27 ºC dan RH 87-95 %. Parameter kinetik yang dipelajari adalah pertumbu-han biomasa yang diukur dengan protein biomasa, viable count, konsentrasi spora, laju produksi CO , kehilangan air 2dan kehilangan bahan kering serta aktivitas total enzim ekstriaseluler kasar terhadap AFB1. Enzim kasar diekstraksidari dedak terfermentasi dengan menggunakan buffer fosfat 0,05 M. Reaksi degradasi AFB1 dilakukan pada suhu 30ºC selama 1 jam dengan menggunakan AFB1 murni sebagai substrat. Hasil penelitian menunjukkan bahwa pertumbu- han biomasa berbeda antara yang diukur dengan viable plate count dan dengan pengukuran protein biomasa. Pada hasil plate count menunjukan pertumbuhan biomasa terjadi sampai hari ketiga fermentasi dan relatif konstan setelah periode tersebut, sedangkan dengan protein biomasa pertumbuhan terjadi sampai hari kelima fermentasi, dan terus sedikit meningkat pada periode berikutnya dengan maksimum protein biomasa 2,628 mg/g bahan kering. Laju pertum- buhan spesifik adalah 0,022/jam, dan laju produksi CO  tertinggi adalah 0,0324 mmol/g/hari dan dicapai pada hari 2ketiga fermentasi. Aktivitas metabolisme juga ditandai dengan laju kehilangan bahan kering, degan laju tertingi pada hari ketiga fermentasi 0,035 g/g bahan kering/hari. Hubungan antara kehilangan bahan kering dengan produksi CO dinyatakan dengan persamaan y = 1,185 x + 0,0079. Hasil ini menunjukkan bahwa aktivitas metabolik (laju produksi CO  dan jalu kehilangan bahan kering) dapat dipakai untuk mengukur pertumbuhan biomasa. Aktivitas total enzim ekstraseluler tertinggi juga dicapai pada hari ketiga fermentasi, yakni 1,699 µgAFB1/ml/jam, atau 0,888 µg AFB1/gprotein biomasa/jam.


Keywords


Kinetika pertumbuhan; Aspergillus oryzae; substrat padat; aktivitas enzim; aflatoxin B1

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DOI: https://doi.org/10.22146/agritech.9785

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